1. Field
The present invention relates to a speed change apparatus for a vehicle.
2. Description of the Related Art
Conventionally, there has been disclosed an AMT (automated manual transmission) vehicle provided thereon with a three-stage capacity clutch in which three stages of clutch capacity (a clutch full capacity, a higher intermediate capacity, and a lower intermediate capacity) can be selected (see, for example, PCT Patent Publication No. WO 2014/157631 (Patent Document 1)). In the speed change apparatus of Patent Document 1, during clutch difference rotation absorption for absorbing a difference rotation between a clutch outer (on the engine side) and a clutch center (on the transmission side) at the time of a shift, it is possible to select the higher intermediate capacity and the lower intermediate capacity as the clutch capacity, in consideration of the rear wheel driving force after the shift on the basis of throttle position, etc. Though not disclosed in detail in Patent Document 1, during absorption of the clutch difference rotation, a retard control of ignition (a control for temporarily lowering the engine output) is performed in order to prevent so-called “blow-up” in which the engine rotational speed rises rapidly.
Meanwhile, such a speed change apparatus as disclosed in Patent Document 1 has some problems on a control basis during the period around the completion of the clutch difference rotation absorption.
Problem 1: During the difference rotation absorption at the time of shifting-up, the output on the engine side is in a lowered state due to a retard control of ignition, although the rotational speed is higher on the engine side than on the transmission side. Therefore, when the rotational speed of the clutch outer and that of the clutch center are synchronized by an intermediate clutch capacity, a deficiency in power on the engine side and the corresponding lowering in the driving force may be generated immediately after the synchronization.
Problem 2: If the retard control of ignition is returned (finished) in an intermediate clutch capacity state before completion of the difference rotation absorption, for the purpose of solving Problem 1, a rise in the engine output may cause blow-up of the engine, whereby the difference rotation being decreased by synchronization may be enlarged.
Problem 3: If the retard control of ignition is returned (the engine output is returned to a normal output) and the clutch capacity is brought to a full capacity before completion of the difference rotation absorption, in order to solve Problems 1 and 2, an acceleration vibration (variation in acceleration of the vehicle; so-called shift shock) may be generated, depending on the operating conditions such as throttle position.